This invention relates to an ink and fabric combination in ink jet printing, and more particularly, to an ink/fabric combination that produces more durable, water-fast and wash-fast images.
Dyeing of fabrics with anionic dyes, particularly fabrics containing polyamide fibers is known. Anionic dyes such as acid dyes and pre-metallized dyes are widely used for the dyeing of polyamide fibers in which the nitrogen containing groups of the polyamide fibers such as nylon and hydroxy groups of the cellulose fibers such as cotton, rayon etc. serve as the dye sites.
Conventionally, the dyeing of fabrics involves immersion of the fabric in an aqueous bath containing a solution of the dye after the fabric has been pretreated by treatments well-known in the art. Typically all the dye used in the process is added to the bath prior to immersion of the fabric; that is, the bath is at "full strength" prior to immersion of the fabric. The bath is then typically raised to an elevated temperature, often as high as the boiling point at ordinary atmospheric pressure. At times, dyeing is done at extreme temperatures using autoclaves.
In an alternate process, disclosed in U.S. Pat. No. 5,230,709, the bath containing the fabric is first raised to a temperature characterized as a "transition temperature" for the particular polyamide. The dye solution is then introduced to the bath in aliquots in such a way that the polyamide fibers are kept "hungry" for dye.
The above processes are used for uniform dyeing of the fabric. For dyeing fabrics to produce a pattern, it is known use a screen printing process for the application of the dye.
Dyes which are used in the processes know in the art are often called small molecule "leveling" dyes. Where good light fastness and/or wash fastness are required, large molecule and pre-metallized dyes are more desirable. Yet, these types of dyes have the disadvantage in that they are structure sensitive, meaning that minor variation in the physical structure of the fibers are revealed in the final dyed product. This is undesirable. It is known to use dye auxiliaries and retarding agents to counteract this defect, but the use of such compounds often inhibit the ability of the fibers to be deeply colored or have dark shades.
Another approach to dyeing polyamides and mixed fiber fabrics, such as polyamides and cotton, makes use of fiber reactive dyes. Such reactive dyes form covalent bonds with free amine end groups of the polyamide fraction and covalent bonds with the hydroxyl groups of the cellulose fraction. One class of reactive dyes are the dichloro-s-triazinyl system. These dyes in aqueous solution can be displaced from solution onto the polyamide by addition of salt (e.g., potassium chloride) and then alkali which fixes the dye with the fiber. Another class are the vinyl sulfone reactive dyes based upon sulfate esters of hydroxysulphonyl dyes. Under alkaline conditions the vinyl sulfone group is generated which in turn reacts with ionized cellulose to form the covalent bond between dye and fiber. As disclosed in U.S. Pat. No. 4,762,524; dyeing of polyamides at the boil with vinyl sulfone reactive dyes is also possible under conditions therein disclosed. As a result, it is know to dye polyamide and cotton blends with appropriately chosen fiber reactive dye systems. In particular, better wash fastness and color fastness for deep shades are obtainable with fiber reactive dyes. However, this process is disadvantageous in that it includes wet processing and the proper disposal of the effluent stream containing unreacted dye adds expense and raises environmental concerns.
Attempts have been made recently to reproduce high quality colored graphic or pictorial information using ink jet technologies for applications such as textile printing. Ink jet printing is a non-impact method for recording information in response to an electronic signal, such as that generated by a computer. In the printer, the electronic signal produces droplets of ink that are deposited on a substrate or media such as paper or transparent film. Such attempts have been met with several challenges. For example, it has proved difficult to accurately reproducing the various hues, tints, and colors contained in a typical colored picture on fabric fabrics using ink jet printers. In addition, the images printed on such fabrics are expected to be durable (crock-fast) and to withstand the rigorous treatments of fabrics, such as laundering.
The processes described above for processing of textile fabric or fibers have several processing limitations and the dyes have their own limitations when it is desired to record a high quality, multicolored image. Color selection is limited because many of the readily available dyes lack color fastness (i.e., the dye tends to fade upon exposure to ultraviolet light) or do not have enough solubility to give the required chroma. Moreover, the tendency of ink droplets to wick or bleed together is an aggravated problem because the printing of a high quality image depends on the formation of small, sharply defined dots of each printed color. While some of the problems associated with dye based inks can be overcome or alleviated to some extent, a need still exists for better inks and/or better treatments or coatings for fabrics or fibers that will be ink jet printed. A specific need exists for such an ink/fabric combination that is capable of reproducing colored pictorial information as a high quality, durable, wash-fast and water-fast image on fabric substrates, thereby meeting the requirements for textile printing.